I know for sure he is bride collie as his mom is a beautiful pb border. Unfortunately she was a puppy mill dog and was bred very young. We are not sure if she was bred with another bc or not. He does resemble a flat coated retriever. However, he looks so much like our last boy, Lucky, who was a bc/black lab. I belong to a bc forum. Some of the pb dogs are large like him and have coats like his so I guess we will never know. It doesn't matter to me if he is pb or what he is. He is my special boy. He has a lot of anxiety which is a long story but he has come a very long way.
The mill was eventually closed down and Silky and her 11 puppies made their way north to a rescue where they all found their forever homes. Silky lives in Ohio and has a once a year visit here.
Sorry for the long bc story on a chi forum.